Known gear cutting machines 10′ have a machine table 50′ with an associated counter-support 60′ and a counter-bracket arm 30′ or spindle sleeve 30′ mounted thereon (cf. FIG. 2).
The counter-bracket arm 30′ has the function to lower or set down the clamping device upper part 90′, which is not shown in detail, on the workpiece 91′, but in most cases additionally also clamps the workpiece 91′ between the clamping device lower part 92′ and the clamping device upper part 90′. This applies both to undulating workpieces and to bore parts.
In addition, in undulating workpieces there is also a guiding and centering function of the countersupport 60′, i.e. alignment errors of the counter-bracket arm 30′ with respect to the table center of the machine table 50′ have a negative effect on the machining result.
In order to minimize the unproductive idle periods for ancillary processes such as loading and unloading workpieces, clamping workpieces and also for the location-oriented positioning of workpieces, it is likewise known to equip gear cutting machines, above all gear grinding machines, with two machine tables. However, since the ancillary processes now take place in parallel with the machining operation, the problem exists that the ancillary processes can have a disadvantageous effect on the machining result due to the mechanical coupling of the corresponding clamping devices for the workpieces, which however is undesirable and should therefore be avoided.
From EP 1 146 983 B1, such gear cutting machine with a double table is known already.
EP 2 305 409 A1 furthermore discloses a method for operating a gear grinding machine with hanging machine tables for loading and unloading the machine.
EP 1 992 439 A1 relates to a gear cutting machine with a counter-support on a round table.
In the aforementioned approaches known from the prior art the problem exists, however, that ancillary processes can have a disadvantageous effect on the machining result, which however is undesirable and should therefore be avoided.
Therefore, it is the object of the present disclosure to develop a method for operating a machine tool as well as a machine tool in an advantageous way, in particular to the effect that ancillary processes in operation of the machine tool have no or no significant effect on the machining result of the machining process.
In accordance with the present disclosure, this object is solved by a method for operating a machine tool with at least two machine tables, with at least one common counter-support and with at least two counter-bracket arms, the clamping forces acting on a clamped workpiece and/or a workpiece to be clamped are controlled and/or regulated at the respective position in dependence on the current process and in dependence on the process forces necessary according to the current process.
Thereby, it can advantageously be prevented that deformation influences from the clamping operation of workpiece clamping have a negative effect on the machining result of the further workpiece just being machined. In particular, it is possible thereby to minimize movements and deformations of the counter-support, which in ancillary processes occur in parallel with the machining of a first workpiece, as is the case for example during the loading and unloading of a second workpiece, and to reduce or prevent their effects on the machining, so that these deformations cannot have a noticeable negative effect.
The machine tool can be a gear cutting machine, in particular a gear cutting machine by which a toothing can be produced on a workpiece, for example by milling and/or slotting and/or grinding. The gear cutting machine may be a gear grinding machine.
The method for operating a machine tool in particular is a method for actuating a counter-bracket/spindle sleeve function in machines with several machine tables, in particular gear cutting machines with one common counter-support, but several counter-bracket arms.
In addition, it can be provided that on loading and/or unloading the machine tool a workpiece is centered and clamped with a clamping force, wherein the clamping force is dimensioned such that it is large enough to keep the workpiece in position for the workpiece positioning process. For example, the clamping force may be greater than a threshold, the threshold set based on the process.
It is also possible that the machine tool has a loading and unloading position, which is a first position of one of the machine tables, and that all ancillary processes carried out at the loading and unloading position are carried out with reduced clamping force, wherein the clamping force may be dimensioned such that it is large enough to keep the workpiece in position at the loading and unloading position.
Furthermore, it is conceivable that before a movement or during a movement of the workpiece from the loading and unloading position into the machining position the clamping force is increased.
In addition, it is conceivable that during a movement of the workpiece from the machining position, which is a second position of one of the machine tables, into the loading and unloading position the clamping force is reduced.
The increase/reduction of the clamping force always can be effected when the workpiece is not being machined; in the extreme case even during a multi-stage machining operation (on the condition of sufficient machining allowance). In the last step, however, in which the workpiece quality is produced, a deformation of the counter-support must definitely be avoided.
Furthermore, the present disclosure relates to a machine tool, in particular a gear cutting machine, is provided with at least two machine tables, with at least one common counter-support, with at least two counter-bracket arms and with at least one control and/or regulating unit, wherein via the control and/or regulating unit the clamping forces acting on a clamped workpiece or a workpiece to be clamped can be controlled and/or regulated at the respective position in dependence on the current process and in dependence on the process forces necessary according to the current process.
It is also possible that the clamping force is directly and/or indirectly controllable by the control and/or regulating unit such that on loading and/or unloading the machine tool a workpiece can be centered and clamped with a clamping force, wherein the clamping force is dimensioned such that it is large enough to keep the workpiece in position for the workpiece positioning process.
It is furthermore conceivable that the machine tool has a loading and unloading position, which is a first position of one of the machine tables, and that the clamping force is directly and/or indirectly controllable by the control and/or regulating unit such that all ancillary processes carried out at the loading and unloading position are carried out with reduced clamping force, wherein the clamping force may be dimensioned such that it is large enough to keep the workpiece in position at the loading and unloading position.
It is also possible that before a movement or during a movement of the workpiece from the loading and unloading position into the machining position the clamping force is increased and/or that before a movement or during a movement of the workpiece from the machining position, which is a second position of one of the machine tables, into the loading and unloading position the clamping force is reduced.
Further details and advantages of the present disclosure will now be explained in detail with reference to an exemplary embodiment illustrated in the drawing.